lesson 13: chapter 12: nervous system: the membrane potential

electrical potential

difference in concentration of charged particles between one point and another

current

flow of charged particle from one part to another

resting membrane potential (RMP)

charge difference across plasma membrane; typically -70 mV in an unstimulated “resting” neuron

gated channels in the membrane

create electrical currents in the body by flow of ions (Na+, K+, etc.)

leak/passive channels

membrane channels that are always open. these channels are specific for their specific ions

gated channels

channels that are normally closed, but can be stimulated to open, these channels are also specific for its specific ion

three types of gated channels

chemically-gated channel

voltage-gated channel

mechanically-gated channel

chemically-gated channel

binding of a chemical (Ex: hormone, neurotransmitter, etc.) causes the channel to open; found on neuron cell body, dendrites

voltage-gated channel

channel opens due to a change in the membrane potential; found on neuron’s axon, skeletal and cardiac muscle membrane

mechanically-gated channel

channel opens due to physical stress/deformation on the cell’s plasma membrane; found on sensory receptors (touch, pressure, vibration)

inactivated channel

ions cannot pass through the channel, but the channel is not considered “closed” - an “inactivation gate” blocks the channel

resting membrane potential (RMP)

ions are unequally distributed between extracellular fluid (ECF) and intracellular fluid (ICF)

RMP results from the combined effect of

diffusion of ions down their concentration gradients

selective permeability of the membrane

electrical attraction of cations and anions to each other

which ion has he greatest influence on the RMP

potassium (K+) because the cell membrane is more permeable to K+ than others

sodium-potassium (Na+/K+) pup

3 Na+ out

2 K+ on

uses ATP

contributed about -3 mV to the RMP